# Mitochondrial fatty acid oxidation is stimulated by red light irradiation

## TL;DR

Red light boosts energy production in skin cells by activating fatty acid oxidation, while UVA and blue/green light have harmful or neutral effects.

## Contribution

Red light stimulates mitochondrial fatty acid oxidation via AMPK activation in keratinocytes, a novel metabolic response to visible light.

## Key findings

- Red light increases basal and maximal oxygen consumption rates in keratinocytes.
- Red light activates AMPK-dependent fatty acid oxidation and reduces free fatty acid levels.
- UVA light inhibits oxidative phosphorylation, while blue and green light do not.

## Abstract

Keratinocytes are the primary constituents of sunlight‐exposed epidermis. In these cells, ultraviolet (UV) A light completely inhibited oxidative phosphorylation, while equivalent doses of blue and green light preserved metabolic fluxes but reduced viability. In contrast, red light enhanced proliferation and elevated basal and maximal oxygen consumption rates for 48 h without altering protein levels of the electron transport chain. Targeted flux analysis revealed that red light specifically activates AMP‐activating protein kinase (AMPK)‐dependent mitochondrial fatty acid oxidation. This was accompanied by reduced levels of free fatty acids and increased acetyl‐CoA carboxylase phosphorylation. Together, our results characterize wavelength‐selective regulation of keratinocyte metabolism: UV/visible wavelengths induce damage, while red light triggers AMPK‐dependent fatty acid oxidation, providing a mechanistic explanation for photobiomodulation in epidermal cells.

Impact statementSunlight impacts skin cells in surprising ways. While UVA harms energy production and blue/green light reduces survival, red light boosts keratinocyte metabolism. We show that red light activates AMPK‐dependent fatty acid oxidation, enhancing proliferation and energy use. These findings reveal how specific wavelengths can damage or stimulate skin cells.

Sunlight impacts skin cells in surprising ways. While UVA harms energy production and blue/green light reduces survival, red light boosts keratinocyte metabolism. We show that red light activates AMPK‐dependent fatty acid oxidation, enhancing proliferation and energy use. These findings reveal how specific wavelengths can damage or stimulate skin cells.

Light at different wavelengths has distinct effects on keratinocyte viability and metabolism. UVA light abrogates metabolic fluxes. Blue and green light have no effect on metabolic fluxes, while red light enhanced oxidative phosphorylation by promoting fatty acid oxidation.